The invention in particular refers to unicompartmental prostheses. In a known manner, such a prosthesis includes a femoral implant capable of cooperating with a patellar implant or a native patella. The femoral implant includes an outer face whereof the profile enables kinematics of the prosthetic knee close to the original kinematics of the knee, as well as an inner face whereof the profile is critical for the positioning and fastening of the implant to the femur. Once placed, this implant undergoes significant mechanical stresses, in particular biasing the fastening on the bone, during the different operating phases: walking, crouching, etc.
Thus, it is essential for the femoral implant to be positioned precisely on the bone requiring repair, then rigidly and lastingly immobilized. These functions are in particular performed by using bone anchoring means formed on the inner face of the implant, and by inserting surgical cement between the inner face and the bone preparation surfaces of the femur.
Before implanting the prosthesis in the patient, the surgeon performs a bone preparation that corresponds on the one hand to the anatomy of the patient, and on the other hand to an available implant profile. More specifically, the implantation of such a prosthesis requires performing distal and anterior bone preparations of the femur. Under these conditions, it is advantageous to have a set of femoral implants having different profiles and dimensions, so as to choose the implant that is best suited to the anatomy of the patient.
However, different implants may require modifying the bone preparation before the suitable implant can be implanted, which causes lost time and may be detrimental to the quality of the surgical operation. In particular, the implantation of the prosthesis is unsatisfactory and may have negative consequences if, due to its profile and dimensions, the implant is not positioned in a configuration where it is flush with the bone preparation surfaces. FR-A-2 908 040 describes a set of femoral implants for a unicompartmental knee prosthesis. These implants are symmetrical and designed to replace only one of the two compartments, inner or outer, of the femur. Thus, these implants have a relatively simple shape compared with a bi-compartmental implant. The thicknesses of these implants, considered at the distal and posterior inner bearing surfaces, are equal and constant irrespective of the dimensions of the implant, while the lengths of the distal and posterior bearing surfaces may vary between the implants. In other words, the distal and posterior parts of the implants have different dimensions for each implant, which is not satisfactory.
U.S. Pat. No. 5,226,915, FR-A-2 728 782 and FR-A-2 955 482 describe other examples of femoral implants.